The invention relates to a meter pulse initiator and, more particularly, to such a pulse initiator that generates electrical signals corresponding to the rotation of the rotor of a watthour meter.
Electrical utilities typically use watthour meters to measure energy usage at remote consumer locations. Such meters generally operate to rotate a rotor disc at a speed that is proportional to the power usage at the particular romote location. The rotational movement of the rotor disc is coupled to an indicator dial that registers the power usage and the indicator dial is periodically read by a representative of the utility to determine the power consumption at the consumer location.
Such a meter reading process is time consuming and relatively wasteful of manpower since many human meter readers must be employed to service the large number of watthour meters that are installed throughout a power distribution network. In addition, the delays and human error inherent in such a meter monitoring system add to the system's overall inefficiency. Furthermore, such systems are subject to consumer tampering since individual meters are only cursorily inspected at periodic intervals.
Consequently, automatic watthour meter monitoring systems have been devised to constantly monitor the various watthour meters in a network and to thereby increase the efficiency of the monitoring system. Such systems have employed meter pulse initiators for converting the rotary motion of the rotor of a watthour meter to corresponding electrical signals that are transmitted to a central monitoring location.
The U.S. patent to Roe, U.S. Pat. No. 3,127,594, discloses a prior art meter pulse initiator that uses a continuous light source to irradiate the reflecting surface of the rotating rotor of a watthour meter. A phototransistor is employed to detect the light that is reflected from the surface of the rotor. As the rotor rotates, non-reflective marks on the rotor interrupt the radiation from the light source. The phototransistor registers the interruptions of the light and thereby provides electrical signals that correspond to the rotation of the rotor. Other prior art meter pulse initiators employ a hole, commonly called a creep hole, in the rotor to transmit light from a source on one side of the rotor to a detector on the other side of the rotor.
Prior art meter pulse initiators have typically employed continuously energized, high intensity light sources that utilize a substantial amount of power. In addition, the continuous, high intensity operation of such sources has resulted in operational degradation over time, causing increased susceptibility to noise-related errors.
Also, many of such pulse initiators have reduced reliability due to the effects of ambient light, thermal current errors inherent in such devices as phototransistors, and measurement errors induced by rotor vibration or reference jitter.
Moreover, many prior art meter pulse initiators are susceptible to willful tampering by the use of bright lights such as flood lamps or pulsed lights such as strobe lamps, as well as unintentional jamming by sunlight and sources of artificial illumination.
Accordingly, it is an object of the invention to provide a simple and effective means to fit a watthour meter with an optical meter pulse initiator that provides an electrical signal output that is proportional to power useage.
A further object of the invention is to provide such a meter pulse initiator that will operate with a light signal of greater intensity to reduce the effect of ambient illumination.
Another object of the invention is to provide a positive indication of the rotation of the rotor of a meter despite rotor vibration or reference jitter.
A further object of the invention is to provide a meter pulse initiator having a radiation source that normally operates at reduced power to save energy and that operates at increased power levels to provide intense radiation when a creep hole moves between the radiation source and an associated radiation detector.
These and other objects of this invention will become apparent from a review of the detailed specification which follows and a consideration of the accompanying drawings.